CFSv2 Seasonal SSTs (clim19912020)
first  rec: avg(lastbs-1, lastobs, CFSv2 month 1)
second rec: avg(lastbs, cfs month 1, CFSv2 month 2)
last   rec: CFSv2 month 9
other  rec: CFSv2 3-mo average
 TrgSeason    SST34
   202309     1.38
   202310     1.40
   202311     1.44
   202312     1.57
   202401     1.59
   202402     1.45
   202403     1.26
   202404     1.06
   202405     0.74
   202406     0.29